1. Field of the Invention
The present invention relates to an image forming apparatus in which time taken to return from a sleep state is reduced, a method of controlling the image forming apparatus, and a storage medium.
2. Description of the Related Art
In recent years, an increasing number of image forming apparatuses have come to be provided with a sleep mode in which when the apparatus is not in use by a user, the image forming apparatus is only partially energized thereby preventing electric power from being supplied to components unnecessary for the multifunction peripheral to return from the sleep mode.
It is desirable that return from the sleep mode (hereinafter referred to as “return from sleep”) takes a short time period. However, with improvement in the performance of each of devices forming an image forming apparatus and the function of an OS, the number of devices that require return processing has increased and the number of stages of return processing executed by an OS has also increased. Therefore, simple execution of the return from sleep tends to increase time taken to complete the same.
This can cause degradation of response of the image forming apparatus, resulting in degraded user-friendliness of the same.
In the return from sleep, it takes time in units of seconds before the backlight of an LCD touch panel provided in an image forming apparatus is turned on after starting a process for the return from sleep. For example, an image forming apparatus performs the process as follows: After initializing hardware devices and an OS, screen data to be rendered on an LCD touch panel is generated, and a screen to be displayed after the return from sleep is rendered in an image buffer memory, whereafter the LCD touch panel is displayed. Therefore, it takes time in units of seconds before the image forming apparatus completes the process for the return from sleep.
In connection with the above-described technique, there has been disclosed a technique in which when the backlight is turned off, the display density value of the LCD touch panel is automatically adjusted to a larger value than a value set before the turn-off of the backlight (see e.g. Japanese Patent Laid-Open Publication No. 2000-194324).
Further, there has been disclosed a method of increasing the speed of the return from sleep in which initialization of an image memory is not executed during return from sleep, and after the entire system is initialized, the initialization of the image memory is started as background processing (see e.g. Japanese Patent Laid-Open Publication No. 2001-111797).